1. Field of the Invention
The present invention relates to an electroacoustic transducer.
2. Description of the Related Art
Electroacoustic transducers which operate in accordance with the electrodynamic principle include a diaphragm which is connected to a foil. The foil protrudes into the annular slot between the poles of a magnet and the movement of the coil produces the conversion of acoustic energy into electrical energy, or vise versa.
In order to achieve a high efficiency and a good quality with respect to a low distortion factor, it is desirable that the movement of the coil takes place within a portion of the magnetic field in which it is has the highest possible intensity and a good linearity, i.e., in the air gap of the magnet yoke itself.
Another requirement to be made of the diaphragm or its surroundings is that the diaphragm is to be capable of freely moving within an amplitude which is as large as possible, without making contact with any structural components. This requirement is contradictory to the first requirement because the coil itself is seated on the diaphragm and, thus, the yoke of the magnet must also be located close to the diaphragm which, in turn, significantly limits the freedom of movement of the diaphragm in the direction of the magnet.
In order to eliminate this problem, it has become known in the art to glue a coil carrier onto the diaphragm, wherein the coil carrier essentially has the shape of a cylindrical casing and includes an adhesive edge to be glued to the diaphragm. At a distance from the diaphragm, the coil is then glued to the coil carrier, so that the diaphragm may have a greater distance from the magnet, while the coil is still located in the best possible position in the magnet yoke. Although this solution appears to be excellent at first glance, it is difficult to realize: An additional component, namely, the coil carrier, is required. This coil carrier must be glued to the diaphragm which results in problems with respect to manipulation because the diaphragm is comprised of a sensitive thin skin, i.e., conventional thicknesses of diaphragms are in the order of magnitude of 40 micrometers or frequently even thinner, which makes it necessary as a result to mount the coil on the diaphragm carrier; this is also extremely problematic because it is not easy to secure the diaphragm carrier. In addition to all of that, there are tolerance and adjustment problems caused by the additional structural component which cannot be ignored.
All of the problems discussed above occur in a product which is usually manufactured with a high cycle speed, wherein cycle speeds of 6 seconds for each work step are quite conventional, which means that the devices used must meet high requirements. On the other hand, if smaller quantities are manufactured, there are significant problems with respect to gluing, particularly gluing of the coil carrier to the diaphragm, because it is almost impossible to sufficiently apply adhesive without errors to the tiny available gluing surfaces.
Therefore, it is the primary object of the present invention to provide an electroacoustic transducer of the above-described type in which the problems described above are eliminated and a solution is provided which does not require the use of a coil carrier, while still making it possible to arrange the coil father away from the actual diaphragm plane and, thus, to position the coil better in the magnet yoke.
In accordance with the present invention, the diaphragm has in the region of the coil an annular protrusion which is integrally connected to the diaphragm, wherein the coil is attached, preferably glued, to the annular protrusion at a desired distance from the diaphragm.
In accordance with a preferred feature, the attachment is effected end face against end face, which is in contrast to conventional, specifically manufactured coil carriers which support the coil on the outer circumferential surface thereof.
In accordance with another embodiment, the diaphragm has in the area of the coil an annular reinforcing corrugation which is attached to the coil in an appropriate manner, preferably by gluing.
The present invention is based on the finding that it is possible by using the deep-drawing method to shape the diaphragm in such a way that a coil carrier can be formed integrally with the diaphragm material at the same time the diaphragm is manufactured. Since this shaping is effected in the same tool and the same method step as the shaping of the diaphragm, there are no tolerance or adjustment problems. The previously necessary separate coil carrier component is unnecessary and fastening of the coil to the protrusion according to the present invention is as unproblematic as it was in the past to mount the coil directly on the diaphragm without the use of a coil carrier.
Another advantage is the fact that an additional oscillating mass is missing, as it was in the past always formed by the coil carrier; this has a particularly positive effect on the conversion of high frequencies.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of the disclosure. For a better understanding of the invention, its operating advantages, specific objects attained by its use, reference should be had to the drawing and descriptive matter in which there are illustrated and described preferred embodiments of the invention.